This invention relates to systems and methods for processing blood, e.g., for filtration, pheresis, or other diagnostic or therapeutic purposes.
There are many types of continuous and intermittent blood processing systems, each providing different therapeutic effects and demanding different processing criteria.
For example, hemofiltration emulates normal kidney activities for an individual whose renal function is impaired or lacking. During hemofiltration, blood from the individual is conveyed in an extracorporeal path along a semipermeable membrane, across which a pressure difference (called transmembrane pressure) exists. The pores of the membrane have a molecular weight cut-off that can thereby pass liquid and uremic toxins carried in blood. However, the membrane pores can not pass formed cellular blood elements and plasma proteins. These components are retained and returned to the individual with the toxin-depleted blood. Membranes indicated for hemofiltration are commercially available and can be acquired from, e.g., Asahi Medical Co. (Oita, Japan).
After hemofiltration, fresh physiologic fluid is supplied to toxin-depleted blood. This fluid, called replacement fluid, is buffered either with bicarbonate, lactate, or acetate. The replacement fluid restores, at least partially, a normal physiologic fluid and electrolytic balance to the blood. Usually, an ultrafiltration function is also performed during hemofiltration, by which liquid is replaced in an amount slightly less than that removed. Ultrafiltration decreases the overall fluid level of the individual, which typically increases, in the absence of ultrafiltration, due to normal fluid intake between treatment sessions.
Following hemofiltration, fluid balancing, and ultrafiltration, the blood is returned to the individual.
The invention provides systems and methods for achieving synchronized volumetric balancing of fluids in fluid processing procedures during which an outgoing fluid is removed from an individual and an ingoing fluid is supplied to the individual.
One aspect of the invention provides a fluid balancing systems and methods for use in a fluid processing procedure during which an outgoing fluid is removed from an individual and an ingoing fluid is supplied to the individual. The systems and methods make use of a volumetric chamber assembly that communicates with first and second flow assemblies. The first flow assembly supplies a volume of the outgoing fluid and a volume of the ingoing fluid into the volumetric chamber assembly. The second flow assembly discharges a volume of the outgoing fluid and a volume of the ingoing fluid from the volumetric chamber assembly. The systems and methods include a synchronization unit that is coupled to the first and second flow assemblies. The synchronization unit affects a concurrent discharge of the outgoing fluid and ingoing fluid from the volumetric chamber assembly in volumetric balance with a concurrent supply of outgoing fluid and ingoing fluid into the volumetric chamber assembly.
In one embodiment, the volumetric chamber assembly is configured to be selectively placed in operative association with the first and second flow assemblies for use and selectively removed from operative association with the first and second flow assemblies after use.
In one embodiment, the volumetric chamber assembly includes at least one chamber including an interior wall dividing the chamber into a first compartment and a second compartment. The first compartment retains a volume of outgoing fluid. The second compartment retains a volume of ingoing fluid. The interior wall responds to differential fluid pressure to discharge the ingoing fluid from the second compartment as the outgoing fluid is conveyed into the first compartment, and vice versa.
Another aspect of the invention provides a system for volumetrically balancing the supply of ingoing fluid to an individual with the withdrawal of outgoing fluid from the individual. The system comprises a first chamber and a second chamber. Each chamber includes an interior wall dividing the respective chamber into a first compartment to retain a volume of outgoing fluid and a second compartment to retain a volume of ingoing fluid. The interior wall responds to differential fluid pressure to displace outgoing fluid from the first compartment as ingoing fluid is conveyed into the second compartment and vice versa.
According to this aspect of the invention, the system includes first and second flow control assemblies. The first flow control assembly communicates with a source of outgoing fluid and the first compartments of the first and second chambers. The second flow control assembly communicates with a source of ingoing fluid and the second compartment of the first and second chambers.
Further according to this aspect of the invention, the system includes a synchronization unit coupled to first and second flow control assemblies. The synchronization unit is operable in a first cycle, during which the first and second flow control assemblies are commanded to convey a volume of outgoing fluid into the first compartment of the first chamber to displace a volume of ingoing fluid from the second compartment of the first chamber, while conveying ingoing fluid into the second compartment of the second chamber to displace a volume of outgoing fluid from the first compartment of the second chamber. The synchronization unit is also operable in a second cycle, during which the first and second flow control assemblies are commanded to convey a volume of ingoing fluid into the second compartment of the first chamber to displace a volume of outgoing fluid from the first compartment of the first chamber, while conveying a volume of outgoing fluid into the first compartment of the second chamber to displace a volume of ingoing fluid from the second compartment of the second chamber. The synchronization unit operates during the first and second cycles to achieve a predetermined volumetric balance between outgoing fluid and ingoing fluid conveyed through the first and second chambers.
In one embodiment, the synchronization unit is operable in a transition cycle between the first and second cycles. During the transition cycle, the synchronization unit operates the first and second flow control assemblies to prevent flow of both outgoing and ingoing fluids into the respective first and second compartments.
Another aspect of the invention provides a fluid handling system for volumetrically balancing a first fluid with a second fluid. The system comprises a chamber including an interior wall dividing the chamber into a first compartment to retain a volume of a first fluid and a second compartment to retain a volume of a second fluid. The interior wall responds to differential fluid pressure to displace first fluid from the first compartment as second fluid is conveyed into the second compartment and vice versa.
According to this aspect of the invention, a passage conveys fluid into one of the first and second compartments. The passage includes a bypass loop to prevent overfilling of the one compartment.
In one embodiment, the bypass loop includes a pressure relief bypass valve.
Another aspect of the invention provides a fluid handling system comprising a chamber including an interior wall dividing the chamber into a first compartment to retain a volume of a first fluid and a second compartment to retain a volume of a second fluid. The interior wall responds to differential fluid pressure to discharge the second fluid from the second compartment as the first fluid is conveyed into the first compartment. A flow control assembly comprises an inlet valve controlling flow of the first fluid into the first compartment, an outlet valve controlling flow of the second fluid from the second compartment, and a pump to convey the first fluid from a source into the first compartment through the inlet valve. According to this aspect of the invention, a synchronization unit is coupled to the flow control assembly to volumetrically balance flow of the first fluid into the first compartment and discharge of the second fluid from the second compartment.
In one embodiment, the synchronization unit synchronizes the inlet and outlet valves with the pump, such that the volume of the second fluid discharged is less than the interior volume of the chamber.
In one embodiment, the synchronization unit includes a drive assembly that mechanically links together the inlet valve, the outlet valve, and the pump. The drive assembly can, e.g., be ratiometrically linked the inlet valve and the outlet valve to the pump, so that changes in pump speed proportionally changes operation of the inlet valve and outlet valve.
In one embodiment, the pump includes a peristaltic pump having a drive motor. In this arrangement, the synchronization unit includes a cam drive assembly linked to the drive motor that operates the inlet valve and the outlet valve.
Another aspect of the invention provides a method for balancing fluid in a fluid processing procedure during which an outgoing fluid is removed from an individual and an ingoing fluid is supplied to the individual. The method (i) supplies a volume of the outgoing fluid and a volume of the ingoing fluid into a volumetric chamber. The method (ii)
discharges a volume of the outgoing fluid and a volume of the ingoing fluid from the volumetric chamber. The method synchronizes steps (i) and (ii) to affect a concurrent discharge of the outgoing fluid and ingoing fluid from the volumetric chamber in volumetric balance with a concurrent supply of outgoing fluid and ingoing fluid into the volumetric chamber.
Another aspect of the invention provides a method for carrying out hemofiltration. The method (i) operates a hemofiltration machine to convey an individual""s blood through an extracorporeal fluid circuit to a hemofilter to remove waste fluid. The method (ii) conveys the waste fluid from the hemofilter to a first compartment of a chamber. The chamber includes an interior wall dividing the chamber into the first compartment to retain a volume of the waste fluid and a second compartment to retain a volume of a replacement fluid. The interior wall responds to differential fluid pressure to discharge the replacement fluid from the second compartment as the waste fluid is conveyed into the first compartment. The method(iii) supplies replacement fluid into the second compartment. The method (iv) synchronizes steps (ii) and (iii) to volumetrically balance flow of the waste fluid into the first compartment and discharge of the replacement fluid from the second compartment. The method (v) conveys replacement fluid from the second compartment to the individual. The method performing steps (i) to (v) at least four times weekly.
In one embodiment, in step (i), blood is conveyed through the hemofilter at a blood flow rate of at least 300 ml/min.